<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .parent{
            height: 100vh;
        }
        .left{
            float: left;
            width: 200px;
            height: 100%;
            background-color: lightblue;
            text-align: center;
        }
        .right{
            height: 100%;
            text-align: center;
            overflow: hidden;
            background-color: lightcoral;
        }
    </style>
</head>
<body>
    <div class="parent">
        <div class="left">固定宽度</div>
        <div class="right">自适应宽度</div>
    </div>
</body>
</html>